1 /* Concatenate two arbitrary file names. 2 3 Copyright (C) 1996-2007, 2009-2020 Free Software Foundation, Inc. 4 5 This program is free software: you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 17 18 /* Written by Jim Meyering. */ 19 20 #include <config.h> 21 22 /* Specification. */ 23 #include "filenamecat.h" 24 25 #include <stdlib.h> 26 #include <string.h> 27 28 #include "dirname.h" 29 30 #if ! HAVE_MEMPCPY && ! defined mempcpy 31 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N))) 32 #endif 33 34 /* Concatenate two file name components, DIR and BASE, in 35 newly-allocated storage and return the result. 36 The resulting file name F is such that the commands "ls F" and "(cd 37 DIR; ls ./BASE)" refer to the same file. If necessary, put 38 a separator between DIR and BASE in the result. Typically this 39 separator is "/", but in rare cases it might be ".". 40 In any case, if BASE_IN_RESULT is non-NULL, set 41 *BASE_IN_RESULT to point to the copy of BASE at the end of the 42 returned concatenation. 43 44 Return NULL if malloc fails. */ 45 46 char * 47 mfile_name_concat (char const *dir, char const *base, char **base_in_result) 48 { 49 char const *dirbase = last_component (dir); 50 size_t dirbaselen = base_len (dirbase); 51 size_t dirlen = dirbase - dir + dirbaselen; 52 size_t baselen = strlen (base); 53 char sep = '\0'; 54 if (dirbaselen) 55 { 56 /* DIR is not a file system root, so separate with / if needed. */ 57 if (! ISSLASH (dir[dirlen - 1]) && ! ISSLASH (*base)) 58 sep = '/'; 59 } 60 else if (ISSLASH (*base)) 61 { 62 /* DIR is a file system root and BASE begins with a slash, so 63 separate with ".". For example, if DIR is "/" and BASE is 64 "/foo" then return "/./foo", as "//foo" would be wrong on 65 some POSIX systems. A fancier algorithm could omit "." in 66 some cases but is not worth the trouble. */ 67 sep = '.'; 68 } 69 70 char *p_concat = malloc (dirlen + (sep != '\0') + baselen + 1); 71 char *p; 72 73 if (p_concat == NULL) 74 return NULL; 75 76 p = mempcpy (p_concat, dir, dirlen); 77 *p = sep; 78 p += sep != '\0'; 79 80 if (base_in_result) 81 *base_in_result = p; 82 83 p = mempcpy (p, base, baselen); 84 *p = '\0'; 85 86 return p_concat; 87 } 88